Effect of olivine nano-silica additions on the fresh and hardened behaviour of cement pastes and mortars

The present research aims on elucidating the effects of OnS in the fresh and hardened state of cement pastes and standard mortars. To study the effects of OnS and superplasticizer (SP), rheological measurements and the mini-spread flow test were carried out to assess changes in the viscosity caused by the volumetric substitutions of cement (0.5, 1.5, 3.0, 4.5, 7.0 and 10%). The rheological tests were complemented with isothermal calorimetric measurements and standard tests on the compressive and flexural strength of mortars. The results obtained demonstrated that the addition of OnS increases the viscosity, the yield point and the hydration degree of the cement paste, mainly due to the increase of the total specific surface area. This holds also for the case in which a fix amount of SP is applied. The mechanical tests demonstrated that the optimum amount of OnS in standard mortars to obtain an improvement is between 1.5 and 3.0% by vol. Based on the analysis performed, it was possible to conclude that the OnS acts as an accelerating and pozzolanic agent in concrete